Walking with Beasts - Mammoth Journey

The sixth episode takes place during the last Ice Age of the late Pleistocene. It starts in the peak of the summer. The North Sea has become a grassy plain because the ice at the polar caps has caused the sea levels to drop significantly. Grazing on the plain are herds of woolly mammoths, saiga antelopes, and bison. A clan of Cro-Magnons (identified as humans) is also there spending the summer.

 The central focus of the episode is the migration of the herd of mammoths as they travel 400 kilometers from the North Sea to the Swiss Alps for the winter and then back again in the spring. As the mammoth herd migrates south, the episode shows two large deer, the Megaloceros, fighting for rights to a harem of females. As the male Megaloceros fight, a group of humans ambushes them and kills one. A mother mammoth and her baby are separated from the herd, but survive an encounter with a cave lion. When the herd of mammoths reaches the Swiss Alps, the mother and baby mammoth reunite with their herd. The episode also depicts a clan of Neanderthals, who have especially evolved to survive in the cold climate. One is charged by a woolly rhinoceros, but escapes, in part because of his stocky constitution. The climax of the episode is when the clan of Neanderthals attack the herd of mammoth as they turn back to the north. The Neanderthals are gifted hunters who are able to chase two mammoths off a cliff by using fire and spears, one of them being the matriarch of the herd.

 The episode ends in the Oxford University Museum of Natural History with people looking at various skeletons of some descendants of the animals featured in the series. The camera then pulls back through the roof of the museum until the whole world is visible. The narrator states that, "We have since built museums to celebrate the past, and spent decades studying prehistoric lives. And if all this has taught us anything, it is this: no species lasts forever."